The testing of blood samples in mass screening programs (e.g., testing performed on newborns and individuals remote from the testing center) has introduced a need for greater preservation time of blood samples in a more efficient manner before many types of lab tests can be performed. Currently, blood is preserved through two methods for microscopic or cytometric examination of cells or formed elements. In the first method, blood is preserved in a dry form by spotting on glass slides. The second method includes preservation of wet blood in packages (e.g. in test tubes) having anticoagulant therein. The difficulty with preserving dry blood on glass slides is the blood spot on each glass slide is generally limited to a single testing procedure. Once the blood is spotted on the slide, it cannot be transferred to another slide to perform further microscopic examinations. When a large number of individuals are being tested, this complicates the testing in that each slide needs to be carefully labelled and arranged for indexing. Also, the weight for storage and shipping becomes costly for a large number of glass slides.
The main difficulty with wet blood-in anticoagulant is the limited preservation time before the blood cells begin to fall apart (e.g., through hemolysis or pyknosis). The preservation time of wet blood is generally twenty-four (24) hours for microscopic testing. In mass central screening programs a greater time span than twenty-four hours is desirable for shipping and storage. For example, if a United States lab was being used for mass central screening of blood from Africa or Southeast Asia for Acquired Immunodeficiency Syndrome (AIDS), cells in wet blood samples would fall apart and be unusable for microscopic cell-based testing by the time they reached the lab. Another area with similar concerns in which mass screening of preserved blood is used is with newborns for detection of inherited conditions/disorders.